Method for the electrical bonding of semiconductor components

ABSTRACT

A method is disclosed for electrically bonding a first semiconductor component to a second semiconductor component, both components including arrays of contact areas. In one aspect, prior to bonding, layers of an intermetallic compound are formed on the contact areas of the second component. The roughness of the intermetallic layers is such that the intermetallic layers include cavities suitable for insertion of a solder material in the cavities, under the application of a bonding pressure, when the solder is at a temperature below its melting temperature. The components are aligned and bonded, while the solder material is applied between the two. Bonding takes place at a temperature below the melting temperature of the solder. The bond can be established only by the insertion of the solder into the cavities of the intermetallic layers, and without the formation of a second intermetallic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority to European Patent ApplicationNo. 19181468.0, filed Jun. 20, 2019, the contents of which areincorporated by reference herein in its entirety.

BACKGROUND Technological Field

The disclosed technology is related to electrical bonding ofsemiconductor components such as chips or wafers, in particular to 3Dstacking methods involving fine-pitched solder joints.

Description of the Related Technology

The term “3D stacking” refers to techniques for producing a stack of twoor more electrically interconnected semiconductor dies. Conventionalthermal-compression bonding (TCB) for 3D interconnects often combineselectroplated high melting point metal microbumps, such as bumps formedof Cu or Ni, with lower melting point solder metal like Sn. With abonding temperature at or above the melting point of the solder, theliquid solder quickly reacts with the base metal to form anintermetallic compound joint. For Sn-based solder material, a bondingtemperature higher than 250° C. is needed. However, temperaturesensitive devices, such as advanced memories and image sensors requirelow temperatures for 3D stacking to increase the capacity of memory andthe resolution and quality of images.

Especially for die-to-wafer stacking, and because of the full cycle TCBapplied for each die, the throughput that can be achieved by thermalcompression bonding is becoming too low to meet the present industry'srequirements. The high temperature cycles are also a risk in terms ofthe oxidation of the microbumps of neighboring dies in a die-to-waferbonding process.

Low temperature solutions have been explored, and include the use ofalternative solder materials such as indium-based solder, but thesealternatives have not been able to match Sn-based solder in terms of thereliability of the bond. Another approach is the use of a sharpmicrocone structure on the microbumps to achieve a mechanicalinterlocking between the microcones and a solder material insertedtherein, as described for example in the article “Effect of solder alloycomposition on its solid-state bonding quality with Ni microcones” byZhuo Chen et al., 2015 16th International Conference on ElectronicPackaging Technology. The production of Ni or Cu microcones howeverrequires carefully controlled electroplating conditions. Also, thethroughput achievable with this approach is still rather low. Theabove-cited document reports a bonding time of 60 s for example.

International Patent Publication No. WO2010/031845 describes a methodwherein a brittle intermetallic layer is formed on the microbumps of oneof the dies which are to be bonded, the intermetallic having a highroughness so that it breaks upon contacting a solder material applied tothe microbumps of the other die. Bonding takes place at a temperaturebelow the melting temperature of the solder, but high enough so that thesolder is sufficiently soft to enter cavities defined by the roughnessof the intermetallic layer, when a bonding pressure is applied. A secondintermetallic layer is then formed at the interface between the soldermaterial and the first intermetallic layer. Whereas the latter documentincludes examples of a bonding process taking place at temperaturesbelow 150° C., the bonding time is consistently high, in the order of 10minutes or more. This is inconsistent with the industry's present-daythroughput requirements.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

Various aspects of the disclosed technology provide a method for bondingsemiconductor components which does not suffer from the above-describeddrawbacks. A technological improvement is achieved by the methods asdisclosed herein.

The disclosed technology is related to a method for electrically bondinga first semiconductor component to a second semiconductor component,both components including arrays of contact areas. Prior to bonding, alayer of an intermetallic compound is formed on each of the contactareas of the second component. The roughness of the intermetallic layeris such that the intermetallic layer includes cavities suitable forinsertion of a solder material in the cavities, under the application ofa bonding pressure, when the solder is at a temperature below itsmelting temperature. The method includes the alignment and bonding ofthe components, while the solder material is applied between the two.Bonding takes place at a bonding temperature below the meltingtemperature of the solder and under the application of a bondingpressure. According to the disclosed technology, the bond is establishedonly by the insertion of the solder into the cavities of theintermetallic layers, and without the formation of a secondintermetallic layer.

This allows to realize a strong bond in a significantly shorter bondingtime compared to prior art methods. Stated in another way, the bondingtime is chosen so that essentially no second intermetallic is formedduring the bonding time. Despite this short bonding time, the obtainedbond has the same or better bond strength and electrical characteristicscompared to prior art methods. The realization of the strong bond by noother means than the mechanical insertion of the solder into thecavities may be facilitated by certain characteristics of the morphologyof the intermetallic layer.

The disclosed technology is in particular related to a method forbonding a first semiconductor component to a second semiconductorcomponent, wherein both components include an array of contact areas,which are to be bonded together to form electrical connections, andwherein:

-   -   the contact areas of the first component include at least an        upper layer formed of a first contact metal,    -   the contact areas of the second component include at least an        upper layer formed of a second contact metal which may be the        same or different than the first contact metal,    -   on the contact areas of the second component, respective        intermetallic layers are provided, formed of an intermetallic        compound, wherein the roughness of the intermetallic layers is        such that the intermetallic layers include cavities suitable for        insertion of a solder material in the cavities, under the        application of a bonding pressure, when the solder is at a        temperature below its melting temperature,    -   and wherein the method includes:        -   applying a bump of the solder material to each of the            contact areas of the first component,        -   aligning the array of contact areas of the first component            to the array of contact areas of the second component, the            array of contact areas of the second component being            provided with the intermetallic layers,        -   bonding the first component to the second component under            the application of a bonding pressure, at a bonding            temperature below the melting temperature of the solder,            thereby realizing the insertion of the solder material into            the cavities of the intermetallic layers, wherein the            bonding pressure and temperature are applied during a            bonding time,        -   wherein the bond is established only by the insertion of the            solder material into the cavities, and without the formation            of a second intermetallic layer during the bonding time.

According to an embodiment, the solder material is a metal and theintermetallic compound includes or consists of the contact metal of thesecond component and the solder.

According to an embodiment, the method for forming the intermetalliclayers on the contact areas of the second component includes:

-   -   providing the second component,    -   applying on the upper layers of the contact areas of the second        component, the upper layers being formed of the second contact        metal, a layer of a third metal that is different from the        second contact metal, and    -   annealing the second component to thereby form the intermetallic        layers by interdiffusion of the third metal and the second        contact metal.

According to an embodiment, the solder material is a metal, and thethird metal is the same as the solder metal.

The bonding time may be less than 10 seconds, more preferably less than5 seconds.

According to an embodiment, the intermetallic layers are characterizedby plate-shaped grains having a length, and the average length of thegrains of the intermetallic layer is between 0.5 μm (micrometer) and 2μm (micrometer).

According to an embodiment, the skewness of the intermetallic layers ispositive, and the normalized volume of the intermetallic layers isbetween 0.3 μm³/mm² (cubic micrometer per square millimeter) and 0.8μm³/mm².

According to an embodiment, the contact metal on the second component iscobalt, the solder material is Sn and the intermetallic compound isCoSn₃.

In the case where the contact metal on the second component is cobalt,the solder material is Sn, and the intermetallic compound is CoSn₃, theintermetallic layers may be formed as described above, and the annealingstep may be performed at a temperature between 150° C. and 270° C.

In the case of the intermetallic compound being CoSn₃, the bonding timemay be about 2 seconds, the bonding temperature about 150° C. and thebonding pressure about 46 MPa.

According to an embodiment, the intermetallic layers are applied equallyto additional contact areas of the second component and theintermetallic layers are passivation layers which protect the additionalcontact areas from oxidation during the bonding step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1G illustrate the method of the present disclosureaccording to one embodiment.

FIG. 2 illustrates an example morphology of the intermetallic layerproduced in accordance with the present disclosure.

DETAILED DESCRIPTION OF CERTAIN ILLUSTRATIVE EMBODIMENTS

The present disclosure will be described on the basis of an exampleembodiment(s), which is not intended to limit the scope of the presentdisclosure. The embodiment concerns the formation of a bond using Sn asthe solder, Co as the contact metal on the first and the secondcomponent, and CoSn₃ as the intermetallic compound formed on the secondcomponent prior to bonding. The CoSn₃ intermetallic may be formed byannealing of the second component, after application of a Sn layer onthe Co contact areas of the second component. This method is illustratedin FIGS. 1A to 1D. In FIG. 1A, the first component 1 is shown, which maybe a silicon die 2 including an array of contact areas 3. At least theupper layer of the contact areas 3 is formed by patches of Co having athickness in the order of several micrometers, for example 5micrometers. Sn solder bumps 4 are applied to the contact areas 3, asshown in FIG. 1B. The bumps 4 may be produced by electroplating. Thethickness of the solder bumps 4 may be applied using any suitablemethods, for example in the order of 4 to 7 micrometers.

As seen in FIG. 1C, the second component 10 may be a silicon wafer 11including an array of contact areas 12 being similar in size andthickness to the contact areas 3 on the first component 1, and spacedapart at the same distances than the contact areas 3 on the firstcomponent. The contact areas 12 also include at least an upper layer ofCo having a thickness in the order of micrometers. As shown in FIG. 1D,a thin layer 13 of Sn is deposited on the Co upper layers of the contactareas 12 of the second component, for example by electroplating. Thethickness of the Sn layer 13 is preferably in the order of 500 to 1000nm, but other thicknesses can be suitably implemented.

The second component 10 is then subjected to a thermal treatment, bymaintaining the component at an annealing temperature during a giventimespan, the result of which is illustrated in FIG. 1E. The annealingtemperature is preferably in the range between 150° C. and 270° C., butother temperatures can be suitably implemented. Under the influence ofthe elevated temperature, interdiffusion of Co and Sn takes place and alayer 14 of the intermetallic compound CoSn₃ is formed on each of thecontact areas 12. The intermetallic layer 14 is symbolically drawn withvisible peaks and valleys to indicate that it is a layer with a highroughness. According to some embodiments, the RMS roughness is about 250nm or more when the thermal treatment is performed at an annealingtemperature in the lower end of the 150-270° C. range, to about 450 nmor more for an annealing temperature in the higher end of the range. Thepeak-to-valley height of the intermetallic layer 14 is between 1micrometer and 2 micrometer or more, also as a function of increasingannealing temperatures within the range 150-270° C. The anneal timesdecrease for increasing temperatures, from several hours (e.g., 3 hours)at 150° C., to about one minute at 270° C.

The Sn layers 3 are essentially fully consumed during the formation ofthe intermetallic layers 14 while the thickness of the Co patches in thecontact areas 12 is reduced very little. The thickness reduction ratioto form the CoSn₃ for Co and Sn solder is 0.14 and 0.97 respectively,based on the density and molar volumes of each phase. The high thicknessreduction ratio of Sn solder and low thickness reduction ratio of Coenables the full formation of CoSn₃ with limited Co thickness reduction.

Reference is then made to FIG. 1F. The second component 10 is attachedto a chuck 15. By a bonding tool 16 or any suitable tool, the firstcomponent 1 is then bonded to the second component 10. The arrays ofcontact areas 3 and 12 on the first and second component are aligned,and the solder bumps 4 on the first component 1 are brought intophysical contact with the intermetallic layers 14 of the secondcomponent 10, at an elevated bonding temperature and under theapplication of a bonding pressure. The bonding temperature is lower thanthe melting temperature of the solder (231° C. in the case of Sn), buthigh enough to soften the solder so that the solder is inserted into thecavities formed by the roughness of the intermetallic layer 14.Preferred bonding temperatures applied in the method of the presentdisclosure are lower than 150° C., more preferably between 100 and 150°C., more preferably between 100° C. and a temperature lower than 130° C.The bonding pressure applied may be comparable to the bonding pressureapplied in prior art methods, for example between 20 and 80 MPa.

The bonding time applied in the method of the present disclosure (i.e.,the timespan during which the bonding pressure and bonding temperatureare applied), is significantly shorter than in prior art methods. In thecase of the Co/Sn bond described above, a strong bond is establishedafter bonding times in the order of seconds, for example 2 seconds foreach die. During this time, substantially no chemical reaction takesplace between the solder bumps 4 and the intermetallic layers 14, i.e.,no second intermetallic is formed, and the bond is established only bythe mechanical insertion of the softened solder into the cavities of theintermetallic layers 14. By applying the above-described Co/Sn bondingmethod according to the present disclosure, die shear strengths areobtainable between 10 and 20 MPa.

Without being bound by any particular theory, it is believed that therealization of a strong bond in a short bonding time is at least partlyenabled by the morphology of the intermetallic layers 14. The grains ofthe CoSn₃ layers 14 are shaped as elongate plates defined by the lengthof the grains, measurable on a microscopic image of the intermetalliclayers. For the CoSn₃ intermetallic layers 14, the inventors of thepresent disclosure recorded an average grain length in the order of 1micrometer. A higher average grain length, about 1.4 micrometer wasmeasured for the CoSn₃ intermetallic layers obtained at the higherannealing temperature of 270° C., while an average grain length of about1 micrometer was measured for the lower annealing temperature of 150° C.According to some embodiments of the present disclosure, the morphologyof the intermetallic layer 14 is defined by plate-shaped grains definedby an average grain length between 0.5 and 2 micrometer. According tofurther embodiments, the average grain length is between 0.7 and 1.8micrometer, and between 0.9 and 1.5 micrometer.

Also, the morphology of the intermetallic CoSn₃ is characterized by asurface aspect illustrated in FIG. 2. The skewness of the surface ispositive. The inventors measured the normalized volume of the CoSn₃intermetallic layer. The normalized volume is the ratio of the volume ofthe peaks 20 on a given surface area, to the surface area. Normalizedvolume is expressed in cubic micrometers/square millimeter (μm³/mm²).See below for a description of the measurement and results. According toone embodiment, the morphology of the intermetallic layer 14 is definedby a positive skewness, and by a normalized volume between 0.3 μm³/mm²and 0.8 μm³/mm².

The short bonding time and low bonding temperatures which are applicablein the method of the present disclosure are advantageous also in termsof protecting the contact areas of neighboring dies against oxidation.According to some embodiments, the intermetallic layer 14 is itself apassivation layer that protects these neighboring contacts fromoxidation. This is the case in particular for CoSn₃. It is thereforeadvantageous in this case to produce the intermetallic layer 14 on aplurality of arrays of contact areas 12 on the second component, priorto bonding multiple dies sequentially to the plurality of arrays.

The method is not limited to the application of the above-namedmaterials Co and Sn. The solder could be another material than thecontact metals of the contact areas 3 and 12 of the respectivecomponents 1 and 10. These latter contact metals could be different fromeach other. In the above-described thermal treatment for obtaining theintermetallic layers 14, the layer 13 applied to the contact areas 12 ofthe second component could be formed of a metal that is different fromthe solder material. The method for obtaining the intermetallic layers14 could be different from the above-described thermal treatment. Theintermetallic layers 14 could be deposited on the contact areas 12, forexample by sputtering. The intermetallic layers could be depositeddirectly on the contact areas 12 or one or more intermediate layers maybe deposited first, for example an adhesion layer for improving theadhesion of the intermetallic layers 14 to the contact areas 12.

After realizing the bond by any of the methods described above, anunderfill material may be added to be assembly of the bonded components,in any suitable manner.

Experimental Results

A first and second chip were provided, each having arrays ofCo-microcontacts with a pitch of about 20 micrometers. A Sn soldermaterial bump of about 5 μm was deposited on the Co contacts of thefirst chip by electroplating and a thin Sn layer (about 1 micrometerthick) was deposited on the Co contacts of the second chip. The thin Snlayer reacted with the Co contact areas to form an intermetallic layerat 270° C. within 1 minute. Then the two chips were placed face-to-faceand bonded at about 150° C. with a pressure of 46 MPa. The bonding timewas 2 seconds. After bonding, the cross-section of the bonded interfacewas studied by scanning electron microscopy and electrical connection ofdaisy chains with 800 fine pitch microbumps were carried out in order toinvestigate the bonding yield and quality of fine pitch solder joint.More than 90% electrical yield was obtained. From the cross-section SEMimages, it was found that the Co/Sn intermetallic was successfullybonded to the Sn solder and there were essentially no voids or seamsbetween them. The die shear strength was determined to be about 17 MPa.

The normalized volume was measured on CoSn₃ intermetallic layersobtained at annealing temperatures of 150° C. and 270° C. Themeasurement was derived from a 3D image of the surface roughness of therespective samples on a scale that allows to visualize the peaks shownin FIG. 2. The image was obtained using optical profiling. An opticalprofiling tool provides a very detailed image of the three-dimensionalsurface topography by combining an interferometer and a microscope. Aninterferometer is an optical device that divides a beam of light exitinga single source (like a laser) into two beams and then recombines themto create an interference pattern. Combined with the microscope, opticalprofiling can offer a 3D surface topography phase map. The tool used forthe measurements on the CoSn₃ intermetallic layer was the Veeco Wyko®NT3300™ optical 3D profiling system. All measurements were done in VSImode (Vertical Scanning interferometry). VSI uses a white light sourceand is used to characterize relatively rough surfaces (Ra greater than0.1 mm) or surfaces with discontinuities on steps greater than 160 nm(¼). The measurement range is 2 mm. VSI is accurate down to a fewnanometers, making the method well-suited for applications in MEMS andsemiconductor measurements. During the measurement, the system movesvertically to scan the surface at varying heights and an interferencesignal for each point on the surface is recorded. The measured area was60 micrometer by 50 micrometer with spatial resolution 0.08*0.05micrometer. The vertical resolution was 3 nm. The normalized volume wasdirectly read out from the Veeco analysis software once the measurementwas finished. Measurements were performed at 4 positions, and averagedout. The results are summarized in the following table.

Intermetallic Intermetallic formed at Normalized formed at Normalized150° C. volume μm³/mm² 270° C. volume μm³/mm² Pos 1 0.45 Pos 1 0.69 Pos2 0.39 Pos 2 0.80 Pos 3 0.42 Pos 3 0.71 Pos 4 0.45 Pos 4 0.75 Average0.43 ± 0.03 Average 0.74 ± 0.05 value value

While the disclosed technology has been illustrated and described indetail in the drawings and foregoing description, such illustration anddescription are to be considered illustrative or exemplary and notrestrictive. Other variations to the disclosed embodiments can beunderstood and effected by those skilled in the art in practicing theclaimed invention, from a study of the drawings, the disclosure and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps, and the indefinite article “a” or “an” does notexclude a plurality. The mere fact that certain measures are recited inmutually different dependent claims does not indicate that a combinationof these measures cannot be used to advantage.

What is claimed is:
 1. A method of bonding a first semiconductorcomponent to a second semiconductor component, wherein both componentscomprise an array of contact areas, which are to be bonded together toform electrical connections, and wherein: the contact areas of the firstcomponent comprise at least an upper layer formed of a first contactmetal, the contact areas of the second component comprise at least anupper layer formed of a second contact metal which may be the same ordifferent than the first contact metal, on the contact areas of thesecond component, respective intermetallic layers are provided, formedof an intermetallic compound, wherein the roughness of the intermetalliclayers is such that the intermetallic layers comprise cavities suitablefor insertion of a solder material in the cavities, under theapplication of a bonding pressure, when the solder is at a temperaturebelow its melting temperature, the method comprising: forming theintermetallic layers on the contact areas of the second component;applying a bump of the solder material to each of the contact areas ofthe first component; aligning the array of contact areas of the firstcomponent to the array of contact areas of the second component, thearray of contact areas of the second component being provided with theintermetallic layers; and bonding the first component to the secondcomponent under the application of a bonding pressure, at a bondingtemperature below the melting temperature of the solder, therebyrealizing the insertion of the solder material into the cavities of theintermetallic layers, wherein the bonding pressure and temperature areapplied during a bonding time, wherein the bond is established only bythe insertion of the solder material into the cavities, and without theformation of a second intermetallic layer during the bonding time, andwherein forming the intermetallic layers comprises: providing the secondcomponent; applying on the upper layers of the contact areas of thesecond component a layer of a third metal that is different from thesecond contact metal, the upper layers of the contact areas being formedof the second contact metal; and annealing the second component tothereby form the intermetallic layers by interdiffusion of the thirdmetal and the second contact metal.
 2. The method according to claim 1,wherein the solder material is a metal and wherein the intermetalliccompound comprises the second contact metal of the second component andthe solder.
 3. The method according to claim 1, wherein the soldermaterial is a metal, and wherein the third metal is the same as thesolder metal.
 4. The method according to claim 1, wherein the bondingtime is less than 10 seconds.
 5. The method according to claim 1,wherein the intermetallic layers are characterized by plate-shapedgrains having a length, and wherein the average length of the grains ofthe intermetallic layer is between 0.5 μm and 2 μm.
 6. The methodaccording to claim 1, wherein the skewness of the intermetallic layersis positive, and wherein the normalized volume of the intermetalliclayers is between 0.3 μm³/mm² and 0.8 μm³/mm².
 7. The method accordingto claim 1, wherein the contact metal on the second component is cobalt,the solder material is Sn and the intermetallic compound is CoSn₃. 8.The method according to claim 7, wherein the bonding time is about 2seconds, the bonding temperature is about 150° C. and the bondingpressure is about 46 MPa.
 9. The method according to claim 7, whereinthe third metal is the same as the solder metal.
 10. The methodaccording to claim 1, wherein the contact metal on the second componentis cobalt, the solder material is Sn, and the intermetallic compound isCoSn₃, and wherein annealing is performed at a temperature between 150°C. and 270° C.
 11. The method according to claim 1, wherein theintermetallic layers are applied equally to additional contact areas ofthe second component, and wherein the intermetallic layers arepassivation layers which protect the additional contact areas fromoxidation during bonding.
 12. The method according to claim 1, whereinthe bonding time is less than 10 seconds.
 13. The method according toclaim 12, wherein the intermetallic layers are characterized byplate-shaped grains having a length, and wherein the average length ofthe grains of the intermetallic layer is between 0.5 μm and 2 μm. 14.The method according to claim 13, wherein the skewness of theintermetallic layers is positive, and wherein the normalized volume ofthe intermetallic layers is between 0.3 μm³/mm² and 0.8 μm³/mm².
 15. Themethod according to claim 14, wherein the contact metal on the secondcomponent is cobalt, the solder material is Sn and the intermetalliccompound is CoSn₃.
 16. A method of bonding a first semiconductorcomponent to a second semiconductor component, wherein both componentscomprise an array of contact areas, which are to be bonded together toform electrical connections, and wherein: the contact areas of the firstcomponent comprise at least an upper layer formed of a first contactmetal, the contact areas of the second component comprise at least anupper layer formed of a second contact metal which may be the same ordifferent than the first contact metal, on the contact areas of thesecond component, respective intermetallic layers are provided, formedof an intermetallic compound, wherein the roughness of the intermetalliclayers is such that the intermetallic layers comprise cavities suitablefor insertion of a solder material in the cavities, under theapplication of a bonding pressure, when the solder is at a temperaturebelow its melting temperature, the method comprising: applying a bump ofthe solder material to each of the contact areas of the first component;aligning the array of contact areas of the first component to the arrayof contact areas of the second component, the array of contact areas ofthe second component being provided with the intermetallic layers; andbonding the first component to the second component under theapplication of a bonding pressure, at a bonding temperature below themelting temperature of the solder, thereby realizing the insertion ofthe solder material into the cavities of the intermetallic layers,wherein the bonding pressure and temperature are applied during abonding time, wherein the bond is established only by the insertion ofthe solder material into the cavities, and without the formation of asecond intermetallic layer during the bonding time, wherein theintermetallic layers are characterized by plate-shaped grains having alength, and wherein the average length of the grains of theintermetallic layer is between 0.5 μm and 2 μm.
 17. The method accordingto claim 16, wherein the bonding time is less than 10 seconds.
 18. Themethod according to claim 16, wherein the skewness of the intermetalliclayers is positive, and wherein the normalized volume of theintermetallic layers is between 0.3 μm³/mm² and 0.8 μm³/mm².
 19. Themethod according to claim 16, wherein the contact metal on the secondcomponent is cobalt, the solder material is Sn and the intermetalliccompound is CoSn₃.
 20. A method of bonding a first semiconductorcomponent to a second semiconductor component, wherein both componentscomprise an array of contact areas, which are to be bonded together toform electrical connections, and wherein: the contact areas of the firstcomponent comprise at least an upper layer formed of a first contactmetal, the contact areas of the second component comprise at least anupper layer formed of a second contact metal which may be the same ordifferent than the first contact metal, on the contact areas of thesecond component, respective intermetallic layers are provided, formedof an intermetallic compound, wherein the roughness of the intermetalliclayers is such that the intermetallic layers comprise cavities suitablefor insertion of a solder material in the cavities, under theapplication of a bonding pressure, when the solder is at a temperaturebelow its melting temperature, the method comprising: applying a bump ofthe solder material to each of the contact areas of the first component;aligning the array of contact areas of the first component to the arrayof contact areas of the second component, the array of contact areas ofthe second component being provided with the intermetallic layers; andbonding the first component to the second component under theapplication of a bonding pressure, at a bonding temperature below themelting temperature of the solder, thereby realizing the insertion ofthe solder material into the cavities of the intermetallic layers,wherein the bonding pressure and temperature are applied during abonding time, wherein the bond is established only by the insertion ofthe solder material into the cavities, and without the formation of asecond intermetallic layer during the bonding time, wherein the skewnessof the intermetallic layers is positive, and wherein the normalizedvolume of the intermetallic layers is between 0.3 μm³/mm² and 0.8μm³/mm².
 21. The method according to claim 20, wherein the bonding timeis less than 10 seconds.
 22. The method according to claim 20, whereinthe contact metal on the second component is cobalt, the solder materialis Sn and the intermetallic compound is CoSn₃.